The link at the bottom of this article is a short video that describes what continuity is and how to measure it with a multimeter. In short, an unbroken wire through which electricity can flow is said to "have continuity". Conversely, a broken wire through which electricity is unable to flow is said to "not have continuity". Various electrical components, whether they be fuses or hotend heating elements are designed to work in a particular way. If continuity is broken, the electricity can no longer flow through that component and the component is no longer able to do the thing that it's supposed to. Since breaks in continuity are not always visibly apparent, it's crucial to be able to test it definitively with a meter.
Turn the dial to Continuity Test mode ( ). It will likely share a spot on the dial with one or more functions, usually resistance (Ω). With the test probes separated, the multimeter’s display may show OL and Ω.
If required, press the continuity button.
First insert the black test lead into the COM jack.
Then insert the red lead into the V Ω jack. When finished, remove the leads in reverse order: red first, then black.
With the circuit de-energized, connect the test leads across the component being tested. The position of the test leads is arbitrary. Note that the component may need to be isolated from other components in the circuit.
The digital multimeter (DMM) beeps if a complete path (continuity) is detected. If the circuit is open (the switch is in the OFF position), the DMM will not beep.
When finished, turn the multimeter OFF to preserve battery life.